Reforestation is often carried out by outplanting seedlings that have been grown in seedling nurseries. The seedlings may be bare root stock or, more commonly, the root is enveloped in growth medium in the form of a plug in a containerxe2x80x94this latter is referred to as containerized stock. Outplanting of containerized stock, therefore, involves placing the plug into soil at the reforestation site.
For the purposes of this specification, the term xe2x80x9cplugxe2x80x9d will be considered to include pelletsxe2x80x94for example, Jiffy(trademark) pelletsxe2x80x94and any other suitably retained growth medium, for example, growth medium in multiple cavity containers such as styroblocks. A number of plugs are typically retained in a block. For the purposes of this specification, the term block will, therefore, refer to any container that has a plurality of cavities each which holds a plug. Further, the term xe2x80x9cfertilizerxe2x80x9d will be considered to include both organic and inorganic forms of fertilizer.
To produce containerized stock, the seedlings are seeded directly into the plug, which has been prepared in advance, by filling a plug cavity with a growth medium. Typically, the growth medium is inert and is, for example, comprised of peat or a mixture of peat, vermiculite and sand. As the medium is very low in plant nutrients, fertilizer is provided either as a slow-release fertilizer that is included in the mix, or through fertigation.
Commonly, slow-release fertilizers are available as prills. In this context, xe2x80x9cprillxe2x80x9d is encapsulated fertilizer in the form of a bead. A prill in the context of conifer seedlings growth is chemical or organic fertilizer encased in a polymeric coating made of plastic. Alternatively, granular formulations, both organic and inorganic, may be used that slowly release the fertilizer. These slow-release fertilizers may be added to the plug at the time of sowing with the objective of providing a residual load to the seedling once it is lifted and outplanted. However, regardless of the type of slow-release fertilizer used, much of it has been expended by the time the seedling is ready to be lifted.
Once a seedling reaches the prescribed height, caliper and developmental stage, it is lifted. At this time, it may be outplanted directly, as occurs with the xe2x80x9chot liftxe2x80x9d seedlings, or it may be placed in cold storage, where it will remain over the winter. At the end of the cold storage period, the seedling is thawed and outplanted directly into the reforestation site.
Establishment of the seedling in the reforestation site is a critical step in the reforestation process. Hence there has been research on methods of increasing the rate of early growth. Frequently, seedling growth following outplanting is limited by a lack of adequate nutrients.
Research to increase the availability of nutrients to the seedling following outplanting has been extensive and has focussed on such techniques as co-cultivating mycorhizal fungi with the seedling roots in the nursery, placing fertilizer xe2x80x9ctea bagsxe2x80x9d in a hole next to the hole that the plug is planted into at the reforestation site (U.S. Pat. Nos. 5,022,182 and 5,317,834), and studying root growth to determine ways to increase the seedling""s access to the limited soil nutrients. Limited fertilizer spray programs have also been implemented, but unfortunately, these often result in the brush and weeds outgrowing the seedlings. When this occurs, the brush and weeds have to be controlled, adding further expense to the cost of reforestation.
Despite the concern about the availability of nutrients to the seedling following outplanting, fertilization at lift, rather than at or following outplanting, does not appear to have been actively pursued. Hence the prior art for such an approach appears to be limited to field crop fertilizers, crop seeders and the lifting and packaging equipment currently employed in seedling nurseries.
There are many patents that disclose devices and methods for injecting materials, including fertilizer into soil. These have been developed for field crops, and not for containerized crops, such as conifer seedlings. For example, U.S. Pat. No. 5,394,812 discloses a device and method to inject polymeric materials into soil. The invention is based on a fluid delivery system, with pumps and monitors to control the flow rate. The monitor is in the form of a float valve. The fluid with the polymer therein is delivered to a series of apertures by means of a high-pressure pulse.
U.S. Pat. No. 4,907,516 discloses a device and method for pulsed injection of liquid fertilizer into the soil. A solenoid control valve operates intermittently to interrupt the flow of liquid in order to provide liquid fertilizer to the nozzle in a series of short pulses. Penetration of the fertilizer into the soil is dependent upon the force of the jet of liquid through the nozzle.
Seeders for various purposes are known. U.S. Pat. No. 6,237,514 discloses an apparatus and method for disbursing agriculture seeds and other particulate materials into soil. A hopper supplies seeds to pockets that are located on sprocket wheels. The seeds are retained in the pocket by a housing that abuts the sprocket wheels. The number of seeds that are retained in each pocket is dependent upon the seed size and the pocket size. Rotation of the sprocket wheels to an open position in the housing results in release of the seeds. The seeds drop without assistance and land on the soil. Seed bed preparation therefore is carried out separately prior to seeding.
U.S. Pat. No. 6,273,648 discloses apparatus providing even distribution of air-entrained particulate material to headers and ultimately to delivery nozzles. Specifically, the patent discloses a conveyor tube and distribution header for use with pneumatic seeders. Turbulence is used within the conveyer tube to propel the seeds toward the distribution head. The distribution head receives the seeds through a flow inlet and then divides the flow into a number of outlet ports.
Another apparatus for dispensing granular or particulate materials is disclosed in U.S. Pat. No. 5,189,965. The apparatus is designed to uniformly discharge a predetermined quantity of granular material at a predetermined rate of application. A hopper is used to feed a metering system that has a number of rollers with pockets to receive the granular material. As the rollers turn, the granular materials are released into segregated metering channels and are pneumatically propelled through a delivery system. Hence, a continuous stream of granular or particulate materials is dispensed onto the soil.
The nursery industry employs mechanized planters for emblings (somatic embryos) and seeds. Essentially, a dibbler is used to create a depression in the seed bed and seeds or emblyings are dropped into the depression. The seed bed may be a transplant bed. Alternatively, the seeds may be sown directly into the plugs. The plugs are arranged in a block such as a styroblock.
Typical styroblocks are each comprised of a styrofoam-type polymer in the form of a block with plug cavities. The plug cavities are generally slightly conical and are wider at the top of the block, narrowing to a small hole at the bottom of the block. The number of plug cavities is variable, as are the size and volume of the plug cavities; all are dependent upon the stock type that is being grown or the desired specifications of the final product.
The process of lifting the seedlings from the blocks in preparation for cold storage or planting is generally mechanized, although the operation is still done manually at some nurseries. Usually, the block is grasped in a holding device, a series of pins are aligned with the plugs in a row-by-row manner and the pins are pushed into the plugs pneumatically, resulting in extraction of the seedlings in their plugs. The seedlings then fall onto a moving culling bed, where they are manually checked for size and morphology, grouped into sets of seedlings and wrapped as bundles in a plastic-type film, such as Saran(trademark).
To Applicant""s knowledge, fertilization at lift has not previously been integrated into the lifting process. This, in part, reflects the difficulties in developing machinery and methodology that can be integrated into the nursery operations, and that does not damage the seedlings.
At lift, the plugs are small, soft and wet. Furthermore, they are close together, especially in the size 410 blocks (112 plugs of 80 mL), which are the most common block size used. The plugs are easily dislodged from the blocks, as the blocks are designed for easy removal of the seedlings at lift. The styroblocks must be treated with care as they are not very durable or rigid.
The preferred fertilizer for fertilizing conifer seedlings at lift is a slow-release prill or a granular type of fertilizer. The prills are fragile, as the outer coating is usually a thin, plastic polymer. The plastic coating is also hygroscopic and consequently, becomes soft and sticky in high-humidity environments. Similarly, granular fertilizer is hygroscopic and will become soft and sticky in high-humidity environments. Additionally, both granular fertilizer and prills tend to adhere to surfaces when force is applied. This makes mechanical insertion difficult as they will tend to clog the injection tubes.
The seedlings are also fragile. The aerial tissue is frequently tall, with many needles, but little branching. The root system is often quiescent at the time of lift, and therefore more susceptible to damage.
Any mechanized method of application has to accommodate the foregoing constraints.
An aspect of the present invention is a method to modulate plant growth by delivering various selected plant growth modulators (e.g., fertilizer, pesticide, etc.) to a plug at lift. Lift may occur prior to transplanting, as occurs in a transplant nursery, or prior to cold storage, or prior to outplanting. In each case, injection of plant growth modulators into the interior of the plug from the plug""s top surface, as contrasted with deposit of such material onto the surface of the plug, could result in perturbation of the seedling. Examination of seedling morphology indicates that there are a large number of crown roots at the top of the plug. In addition, the location of the stem is variable in the plug and the seedling has substantial aerial tissue. These factors may make it difficult to inject fertilizer into the top of the plug, as damage to any part of the plant including the root system, stem or aerial tissue could reduce outplanting success, measured as survival and growth in the first few years following outplanting. Consequently, injection is preferably into the bottom of the plug. In a preferred embodiment, the present invention provides a method for injection of the plant growth modulator into the bottom of the plug, preferably by pneumatically injecting the plant growth modulator into the plug.
For injection into the bottom of the plug, the blocks are preferentially placed on their sides. This promotes retention of a specific dose of fertilizer; if the blocks are upright and the plugs are injected from below, the fertilizer tends to fall out of the plugxe2x80x94even when all the operations are performed with the seedlings on their side there is loss of fertilizer. Further, more air pressure and a higher air flow would be required to inject from below as compared with injecting from the side. As a consequence, the seedlings should be supported, as they may bend and be damaged if left unsupported.
In order to successfully inject plant growth modulator into the plug, it is preferable to pre-form a bore and a port in the plug. The bore is preferably formed by drilling with a specially formed cavity tool through the bottom of the plug. As the cavity tool reaches the end of its stroke, a distal tip of the cavity tool penetrates a top end of the plug and produces the port. The port allows air to be expelled from the bore. By having a shoulder on the cavity tool between a wide cylindrical body and a narrow distal tip, a mating shoulder is created within the bore. The narrowing of the bore afforded by the shoulder impedes movement of the plant growth modulator from the bore into the port. Further, the smaller diameter of the narrow distal tip and its flexibility reduces the risk of damage by the cavity tool to the seedling in the plug.
In order to optimize the injection procedure, the amount (dose) of plant growth modulator injected into each plug should be controlled. Assuming that a metering system of the sort disclosed in U.S. Pat. No. 5,189,965 is used, the correct dose can be applied by selecting the appropriate metering roller, which forms part of the metering roller system. Each metering roller has pockets sized to deliver a specific amount of plant growth modulator, and different rollers have different pocket sizes. Once the dose has been determined, the appropriate metering roller is used to deliver plant growth modulator to the individual injectors, which deliver the dose to the plug. The delivery is preferably effected using a pneumatic injection system.
Once the plug has been injected, it is preferable to close the bore at the bottom of the plug. Closure can be effected with a bore closer or a paste injector. Closing the bore facilitates retention of the plant growth modulator in the bore.
In a preferred aspect of the invention, drilling with a cavity tool precedes injection of plant growth modulator into the plug.
In a preferred aspect of the invention, drilling occurs in at least one self-contained set of plugs, while at the same time injection is occurring in at least one adjacent self-contained set of plugs, and then the sets are laterally displaced so that the drilled set is positioned for injection, the injected set removed, and a fresh set is positioned in place for drilling, thereby minimizing the time required to drill and inject a series of such plug sets. The xe2x80x9csetxe2x80x9d of plugs may conveniently be a row of plugs in a block, or in a more expensive facility, could be an entire block of plugs, provided that the plugs may be maintained in satisfactory alignment for the drilling and injection operations.
In a preferred aspect of the invention, seedlings are held in a seedling holder to reduce damage to the seedlings during nursery operations. Preferably, the seedling holder is comprised of a series of guides spaced to accept a row of seedlings, that slide between the row and support the aerial tissue of the seedlings.
In another aspect of the invention, the styroblock that holds a set of plugs to be drilled and injected is retained in a block restraint while the bore is drilled in the plug and while the plant growth modulator is thereafter delivered into the bore. Preferably a pre-selected dose of the plant growth modulator is delivered to the injector by a metering roller, and the plant growth modulator is then injected into the bore.
In another aspect of the invention, all the seedlings in a block are supported by the seedling holder, which is comprised of a series of guides and dividers. Preferably the dividers are biased from the guides in an open position to allow the seedling to slide into place, closing onto the guides in the closed position to hold the seedlings. A bore is then drilled in the plugs.
In another aspect of the invention, all the seedlings in a block are supported by the guides of the seedlings holder, and more preferably the seedlings are held by the dividers of the seedling holder. Preferably, a bore is then drilled in the plugs.
In another aspect of the invention, all the seedlings in a container are supported and held by the seedling holder, a bore is drilled in the plug, and the plant growth modulator is injected into the bore.
In another aspect of the invention, all the seedlings in a container are supported and held by the seedling holder, a bore is drilled in the plug, a pre-selected dose of the plant growth modulator is delivered to the injector by a metering roller and the plant growth modulator is injected into the bore.
In another aspect of the invention, the block is retained in a block restraint, all the seedlings in a block are supported and held by the seedling holder, a bore is drilled in the plug and plant growth modulator is injected into the bore. Preferably, a pre-selected dose of the plant growth modulator is delivered to the injector by a metering roller.
In another aspect of the invention, all the seedlings in a container are supported and held by the seedling holder, a bore is drilled in the plug, a plant growth modulator is injected into the bore, and the bore is closed.
In another aspect of the invention, all the seedlings in a container are supported and held by the seedling holder, a bore is drilled in the plug, a pre-selected dose of the plant growth modulator is delivered to the injector by a metering roller and the plant growth modulator is injected into the bore.
In another aspect of the invention, the block is retained in a block restraint, all the seedlings in a container are supported and held by the seedling holder, a bore is drilled in the plug, a plant growth modulator is injected into the bore, and the bore is closed.
In another aspect of the invention, the block is retained in a block restraint, all the seedlings in a container are supported and held by the seedling holder, a bore is drilled in the plug, a pre-selected dose of the plant growth modulator is delivered to the injector by a metering roller, the plant growth modulator is injected into the bore, and the bore is closed.
In a preferred aspect of the invention, the operations of drilling, injecting and closing occur concomitantly and preferably concurrently, each in adjacent blocks or in adjacent rows of a block. Accordingly, it is preferable to align and then restrain the block during drilling. An indexing bar is employed to align the various tools with the plugs, and a clamp holds both a block restraint and a seedling holder in place.
In the preferred aspect of the invention, the operations are automated, and may, for example, be controlled by a micro-controller.
In one aspect of the invention, the plant growth modulator that is injected is a suitable selected granular fertilizer.
In another aspect of the invention, the plant growth modulator is suitable selected fertilizer prills.
In yet another aspect of the plant growth modulator is suitable selected encapsulated biological material selected from the group consisting of bacteria, fungi, nematodes, virus, and combinations thereof.
In another aspect of the invention, the plant growth modulator is a suitable selected pesticide.
In yet another aspect of the invention, the plant growth modulator is a suitable selected growth adjuvant.
In yet another aspect of the invention, the plant growth modulator is hygroscopic.
In another aspect of the invention, the plant growth modulator is a seed.
Note that different types of plant growth modulator may be combined in a single injection, assuming physical, chemical and biological compatibility between the modulators injected.
The present invention has been developed concurrently with the development of apparatus suitable for its implementation. Such apparatus, and the use of the apparatus in conjunction with the method, are preferably characterized by the following features:
In one aspect of the preferred apparatus/method implementation, a plug is prepared for subsequent injection of plant growth modulator into the plug by drilling a bore. The bore is created in the plug by a cavity tool. Penetration and exit of the distal end of the cavity tool through the top of the plug results in the formation of a port for release of air during injection of the plant growth modulator into the bore. The bores are preferably drilled in a row of plugs or other selected set of plugs simultaneously using a corresponding set of aligned drills.
It is preferable to drill a series of plugs using a cavity tool system comprising a series of cavity tools that are positioned along a head and spaced in order to align with the plugs of the container during drilling of the bores.
Preferably, predetermined doses of plant growth modulator are delivered using a metering roller system, comprising a metering roller and a perforated plate. The metering roller has a series of pockets, sized to accept a specific and predetermined amount of plant growth modulator. The metering roller preferably subtends a hopper. Rotation of the metering roller from a first position, wherein the pockets accept plant growth modulator from the hopper, to a second position, wherein the pockets are aligned with perforations in the perforation plate results in plant growth modulator being delivered in specific and predetermined doses to individual injectors.
Each injector is preferably comprised of a pneumatic injection tube, an air delivery tube, a collection chamber and a nozzle. The collection chamber is between the air delivery tube and the nozzle. Plant growth modulator that collects in the collection chamber is air-entrained by injecting air through the air delivery tube and into the pneumatic injection tube in pulses of a predetermined duration and intensity. The air-entrained material is then forced into the plug.
A row of plugs or other selected set of plugs may be injected at the same time using the foregoing or similar injection system. For this purpose, the injection system comprises an aligned series of injectors that are positioned on a head in order to maintain alignment of the injectors with the plugs in the styroblock or other suitable container during injection of plant growth modulator into the bores. Preferably the selection of the set of plugs to be injected is at least a complete row and is matched with the set of plugs to be drilled, so that drilling and injection operations can occur side by side simultaneously; after each such combined drilling and injection step, the block is moved laterally to bring the freshly drilled set into alignment with the injection apparatus while an undrilled set of plugs is brought into alignment with the drilling apparatus, and the procedure is repeated seriatim.
After the plugs have been injected, it is preferable to close the bore. Each bore is closed using a bore closer. Preferably, a set of bores are closed simultaneously using a bore closing system. The bore closing system comprises a series of bore closers that are positioned on a bore closer head and spaced in order to align with the plugs of the container during closing of the bores. Preferably the set of bores to be closed at a given time by the bore closing system is matched to the set of plugs to be drilled and the set of plugs to be injected, so that drilling, injecting, and closing operations may be performed simultaneously on adjacent sets of plugs, and consecutively seriatim as the block is laterally displaced following each such combined operation.
In another aspect of the invention, injection is preferably carried out hydraulically using a hydraulic injector, comprising a pneumatic injection tube, a collection chamber, a nozzle and a hydraulic tube which has, at a distal end, a hydraulic ram. Actuation of the hydraulic ram forces air through the pneumatic injection tube, air-entraining the plant growth modulator in the collection chamber, and releasing it through the nozzle, which is directed into the bore in the plug.
Injection with the hydraulic injector is preferably controlled by, for example, a microprocessor, such that a timed sequence of controlled pulses of air are delivered to the pneumatic injection tube. Each pulse of air causes delivery into each bore in a selected set of one dose of plant growth modulator. After each pulse, the collection chamber of each injector is reloaded with plant growth modulator. The hydraulic injection system preferably comprises a series of injectors that are positioned on a head spaced in order to align with the plugs of the container during injection of the bores.
In yet another aspect of the invention, plant growth modulator is injected using a fluid injector. The fluid injector comprises a fluid delivery tube, a collection chamber, a fluid injection tube and a nozzle. Fluid is injected into the injection tube from the fluid delivery tube, thereby fluid-entraining the plant growth modulator in the collection chamber, and releasing it through the nozzle, which is directed into the bore in the plug. Preferably, a series of plugs are injected using a fluid injection system, which comprises a series of injectors that are positioned on a head spaced in order to align the injectors with the plugs of the container during injection of the bores.
In another aspect of the invention, plant growth modulator is injected by means of a sequence of fluid pulses applied to consecutive rows or other selected sets of plugs. Each pulse of fluid results in delivery via each injector in the set of one dose of plant growth modulator. After each pulse, plant growth modulator is reloaded into the collection chamber of each injector in the set.